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Author name code: krijger
ADS astronomy entries on 2022-09-14
author:"Krijger, J." 

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Title: The New SCIAMACHY Reference Solar Spectral Irradiance and
    Its Validation
Authors: Hilbig, T.; Weber, M.; Bramstedt, K.; Noël, S.; Burrows,
   J. P.; Krijger, J. M.; Snel, R.; Meftah, M.; Damé, L.; Bekki, S.;
   Bolsée, D.; Pereira, N.; Sluse, D.
2018SoPh..293..121H    Altcode:
  This paper describes a new reference solar spectrum retrieved from
  measurements of the satellite instrument SCIAMACHY in the wavelength
  region from 0.24 μ m to 2.4 μ m and its comparison with several
  other established solar reference spectra. The SCIAMACHY reference
  spectrum was recorded early in the mission before substantial optical
  degradation due to the harsh space environment sets in. The radiometric
  calibration of SCIAMACHY, applied in this study, includes a physical
  model of the scanner unit. Furthermore, SCIAMACHY's internal white
  light source (WLS) is used to correct for on-ground to in-flight
  changes. The resultant calibrated solar spectrum from SCIAMACHY is
  in good agreement with several available solar spectral irradiance
  (SSI) references in the visible spectral range. Strong throughput
  losses due to detector icing in the near infrared (NIR) are now
  adequately accounted for. Nevertheless, a deficit with respect to the
  ATLAS-3 composite and SORCE/SIM SSI is observed in the NIR. However,
  the SCIAMACHY solar reference spectrum agrees well with the recently
  re-evaluated SOLAR/SOLSPEC-ISS and recent ground measurements taken
  at Mauna Loa in the NIR.

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Title: Improved Correction for Contamination-Induced In-Flight
    Instrument Degradation of SCIAMACHY
Authors: Snel, R. C.; Krijger, J. M.
2015ESASP.735E..13S    Altcode:
  SCIAMACHY suffers from degradation due to contamination of the scan
  mirror surfaces, optical components in the Optical Bench Module, and
  detector surfaces.We have improved the polarisation and degradation
  description of the instrument as well as the optical ground support
  equipment used for initial on-ground instrument calibration. This
  allows for a consistent model of the instrument for both on-ground
  and in-flight conditions, and for arbitrary amounts of contamination
  of the instrument.Using this model we have re-analysed the in-flight
  calibration and monitoring data to arrive at an improved description
  of the throughput and polarisation sensitivity of SCIAMACHY, for any
  time during its mission.

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Title: The new SCIAMACHY calibration and degradation approach and
    validation
Authors: Krijger, J. M. Matthijs; Snel, R.; Bovensmann, H.; Eichmann,
   K. U.; Noel, S.; Liebing, P.; Richter, A.; Buchwitz, M.; von Savigny,
   C.; Rozanov, A.; Bramstedt, K.; Gerilowski, K.; Vountas, M.; Burrows,
   J. P.; van der Meer, P.; van Hees, R.; Aben, I.; Lichtenberg, G.;
   Slijkhuis, S.; Doicu, A.; Schreier, F.; Hrechanyy, S.; Kretschel,
   K.; Meringer, M.; Hess, M.; Gottwald, M.; Aberle, B.; Scherbakov,
   D.; Gimeno-Garcia, S.; van Gijsel, J. A. E.; Tilstra, L. G.; Lerot,
   C.; Van Roozendael, M.; Dehn Serco, A.; Fehr, T.
2010cosp...38..101K    Altcode: 2010cosp...38..101M; 2010cosp.meet..101K
  This presentation covers the highlights of the radiance, irradiance,
  polarisation and degrada-tion re-characterisation of SCIAMACHY
  and its validation. The imaging spectrometer SCIA-MACHY on ENVISAT
  has been collecting data since launch in 2002. Over the years the
  exposure to space has affected the optical performance and rendered the
  on-ground calibra-tion data increasingly more outdated. As the overall
  calibration quality is continuously being improved through better
  in-flight characterisation and updated algorithms, instrument aspects
  with previously acceptable errors are now in need of improvement. This
  required re-analysis of the on-ground calibration measurements, and
  pivots on measurements which were initially not intended for this
  type of calibration and an improved mirror-model for the scanner
  unit. Ad-ditionally, with the new approach it is possible to derive
  scan-angle dependended degradation-corrected calibration key data for
  the contaminated mirror surfaces in the scanner unit, thus improving
  the radiometric, polarisation, and scan-angle calibration of the
  instrument. We will present the new calibration approach and the first
  results of the validation.

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Title: Observations of Umbral Flashes
Authors: Rouppe van der Voort, L. H. M.; Krijger, J. M.
2003csss...12..607R    Altcode:
  We present observations of oscillations in the chromosphere of the
  umbra of sunspots. The observations were obtained with the Swedish
  Vacuum Solar Telescope (SVST) and the Dutch Open Telescope (DOT)
  on La Palma, comprising spectrograms and filtergrams in the Ca II H
  line. The sawtooth pattern in the spectroscopic time evolution of the Ca
  II H core is shown as well as evidence for a connection between umbral
  flashes and running penumbral waves from image sequences. Running waves,
  coherent over a large fraction of the penumbra, seem to be excited by
  flashes that occur close to the umbra-penumbral boundary. Comparing
  the intensity oscillations in the Ca II H line with TRACE observations
  in the 1600 Å passband, we find a phase difference of approximately
  25 ° with 1600 Å leading the Ca II H intensity oscillation which we
  attribute to complex dynamical behaviour.

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Title: Dynamics of the solar chromosphere IV. Evidence for atmospheric
    gravity waves from TRACE
Authors: Rutten, R. J.; Krijger, J. M.
2003A&A...407..735R    Altcode:
  We study the low-frequency brightness modulation of internetwork
  regions in the low solar chromosphere using simultaneous ultraviolet
  and white-light image sequences from the Transition Region and Coronal
  Explorer (TRACE). The ultraviolet sequences exhibit a slowly varying
  brightness pattern in internetwork regions on which the more familiar
  acoustic three-minute oscillation is superimposed, with about half of
  the peak brightness reached in internetwork grains contributed by the
  low-frequency background. We address the nature of the latter, applying
  two-dimensional Fourier filtering to isolate it from the acoustic
  modulation. Spatio-temporal comparisons and selective time-delay scatter
  correlations between the ultraviolet and white-light low-frequency
  sequences establish that reversed granulation constitutes at most a
  minor part of the ultraviolet background. Fourier analysis shows that
  the meso-scale contribution dominates and consists of atmospheric
  gravity waves.

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Title: La Palma observations of umbral flashes
Authors: Rouppe van der Voort, L. H. M.; Rutten, R. J.; Sütterlin,
   P.; Sloover, P. J.; Krijger, J. M.
2003A&A...403..277R    Altcode:
  We present high-quality Ca II H & K data showing chromospheric
  flashes in sunspot umbrae collected with the Swedish Vacuum Solar
  Telescope, the Dutch Open Telescope, and the Swedish 1-m Solar Telescope
  at the Roque de los Muchachos Observatory on La Palma. Differential
  movies, time slices, spectrograms, and Fourier power maps demonstrate
  that umbral flashes and running penumbral waves are closely related
  oscillatory phenomena, combining upward shock propagation with coherent
  wave spreading over the entire spot. We attribute the flash brightening
  to large redshift by post-shock material higher up. We find no obvious
  relation between umbral dots and umbral flashes.

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Title: Photospheric flows measured with TRACE II. Network formation
Authors: Krijger, J. M.; Roudier, T.
2003A&A...403..715K    Altcode:
  We analyse a 7 d (167 h) sequence of TRACE white-light images with 1
  arcsec angular resolution taken at 1 min cadence. The TRACE resolution
  and the fast cadence allows us to produce maps of the horizontal
  flow fields with high angular (1 arcsec) and temporal resolution (5
  min). The field of view of 128arcsec x 128arcsec (~93 Mm x 93 Mm)
  covers approximately an area of 10 to 30 supergranules. This area
  was followed during solar rotation. Magnetic flux was artificially
  inserted into the successive flow maps in the form of ephemeral
  regions with positive and negative polarity. The emergence rate of 2
  x 10<SUP>22</SUP> Mx h<SUP>-1</SUP> with an average flux per region
  of about 1.1 x 10<SUP>19</SUP> Mx produces a good reproduction of the
  chromospheric network as observed in images taken simultaneously at
  1600 Å. In addition, we show that the quiet network can be maintained
  only if field elements of both polarities are inserted into the flow
  fields. Our analysis suggests that the network is fully replenished
  on a time scale of a day and the lifetimes of the magnetic elements
  are of a similar duration.

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Title: Verification of SCIAMACHY's Polarisation Correction over the
    Sahara Desert
Authors: Tilstra, L. G.; Acarreta, J. R.; Krijger, J. M.; Stammes, P.
2003ESASP.531E..13T    Altcode:
  No abstract at ADS

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Title: Current Status of SCIAMACHY Polarisation Measurements
Authors: Krijger, J. M.; Stammes, P.
2003ESASP.531E..14K    Altcode:
  No abstract at ADS

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Title: The "careers in solar physics" session of the SPM10 meeting
Authors: Aulanier, G.; Parenti, S.; Krijger, J. M.
2002ESASP.506..981A    Altcode: 2002ESPM...10..981A; 2002svco.conf..981A
  During the SPM10 meeting held in Prague (Czech Republic) on September
  9-14, 2002, a half-day 'young session' was organized on the topic
  of careers in solar physics. Several young researchers and senior
  scientists were invited to give oral contributions on the current
  advantages and difficulties attached to the current system for
  post-doctoral contracts. A scientist from USA also presented the
  American system for contractors, and an ESA representative presented
  the official position of ESA regarding funding researchers. From
  the talks as well as from the long open discussion which followed,
  it was widely agreed that several typical rules for EU post-doc
  contracts (their short duration, their mandatory mobility, their
  age limit and their administrative and financial difficulties) not
  only lead to serious problems in the private life of postdocs, but
  essentially can have serious drawbacks on the follow-up of long-term
  scientific developments, and could quickly result in a dramatic loss
  of expertise, from the scale of individual institutes to the European
  scientific community at large. Many participants and most of the young
  researchers naturally agreed that new longer-term, renewable and stable
  contracts are necessary. In order to create such types of contracts,
  several fund raising initiative achieveable by the scientific community
  were discussed. The development of better public outreach initiatives
  on the European scale was a possibility which federated most of the
  participants. The resulting conclusion on this session were transmitted
  to the new board of the Solar Physics Section of the EAS/SPS.

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Title: Origin and evolution of ices around massive young stars
Authors: Krijger, Johannes Mattheus
2002PhDT.......215K    Altcode:
  The thesis Structure and dynamics of the solar chromosphere of
  J.M. Krijger is a study on the behavior of the solar chromosphere,
  the thin layer just above the solar surface (photosphere) visible
  in purple red light during a total solar eclipse. The most important
  result of this thesis is that the chromosphere is filled with acoustic
  and internal gravity waves that travel upward until they collide
  with a canopy of expanding magnetic field. The photosphere is the
  layer of which we see the light with the naked eye. Through this
  layer poke large and small magnetic tubes. Above the photosphere
  and the chromosphere sits the hot solar corona of a few million
  degrees. With observations of among others the space satellite TRACE
  (Transition Region and Coronal Explorer) J.M. Krijger shows that the
  photosphere is dominated by flows of the ambient gas that dictate the
  magnetic field where to go. The possible heating of the chromosphere
  is an important unsolved problem in solar physics. The chromosphere
  forms the transition region between the very hot corona, dominated by
  magnetic fields, and the photosphere where gasflows drag the magnetic
  field along. In this transition region the magnetic field, which in the
  photosphere is still trapped in individual tubes, expands to a canopy
  above which the magnetic field fills the entire space. In this thesis
  it is shown that the chromosphere is dominated by upward propagating
  acoustic waves and a magnetic canopy that changes the dynamics of the
  oscillations. Finally J.M. Krijger shows that the network of magnetic
  field in the chromosphere is formed by magnetic tubes that are swepped
  together by flows in the photosphere.

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Title: Photospheric flows measured with TRACE
Authors: Krijger, J. M.; Roudier, T.; Rieutord, M.
2002A&A...387..672K    Altcode:
  We analyse white-light image sequences taken with the Transition
  Region and Coronal Explorer (TRACE) using an optimised local
  correlation tracking (LCT) method to measure the horizontal flows
  in the quiet solar photosphere with high spatial (1 arcsec) and
  temporal (5 min) resolution. Simultaneously taken near-ultraviolet
  images from TRACE confirm that our LCT-determined flows recover the
  actual supergranulation pattern, thus proving that the topology of the
  horizontal flow distribution and network assembly may be studied from
  long-duration TRACE white-light sequences with our method.

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Title: Structure and dynamics of the solar chromosphere
Authors: Krijger, Johannes Mattheus Thijs
2002PhDT.......228K    Altcode:
  No abstract at ADS

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Title: Dynamics of the solar chromosphere. III. Ultraviolet brightness
    oscillations from TRACE
Authors: Krijger, J. M.; Rutten, R. J.; Lites, B. W.; Straus, Th.;
   Shine, R. A.; Tarbell, T. D.
2001A&A...379.1052K    Altcode:
  We analyze oscillations in the solar atmosphere using image sequences
  from the Transition Region and Coronal Explorer (TRACE) in three
  ultraviolet passbands which sample the upper solar photosphere and
  low chromosphere. We exploit the absence of atmospheric seeing in
  TRACE data to furnish comprehensive Fourier diagnostics (amplitude
  maps, phase-difference spectra, spatio-temporal decomposition) for
  quiet-Sun network and internetwork areas with excellent sampling
  statistics. Comparison displays from the ground-based Ca Ii H
  spectrometry that was numerically reproduced by Carlsson &amp;
  Stein are added to link our results to the acoustic shock dynamics
  in this simulation. The TRACE image sequences confirm the dichotomy
  in oscillatory behaviour between network and internetwork and show
  upward propagation above the cutoff frequency, the onset of acoustic
  shock formation in the upper photosphere, phase-difference contrast
  between pseudo-mode ridges and the interridge background, enhanced
  three-minute modulation aureoles around network patches, a persistent
  low-intensity background pattern largely made up of internal gravity
  waves, ubiquitous magnetic flashers, and low-lying magnetic canopies
  with much low-frequency modulation. The spatio-temporal occurrence
  pattern of internetwork grains is found to be dominated by acoustic
  and gravity wave interference. We find no sign of the high-frequency
  sound waves that have been proposed to heat the quiet chromosphere, but
  such measurement is hampered by non-simultaneous imaging in different
  passbands. We also find no signature of particular low-frequency
  fluxtube waves that have been proposed to heat the network. However,
  internal gravity waves may play a role in their excitation.

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Title: Phase Relations between Chromospheric and Transition Region
    Oscillations
Authors: Krijger, J. M.; Curdt, W.; Heinzel, P.; Schmidt, W.
2000ESASP.463..353K    Altcode: 2000sctc.proc..353K
  No abstract at ADS

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Title: COMPTEL detection of pulsed gamma -ray emission from PSR
    B1509-58 up to at least 10 MeV
Authors: Kuiper, L.; Hermsen, W.; Krijger, J. M.; Bennett, K.;
   Carramiñana, A.; Schönfelder, V.; Bailes, M.; Manchester, R. N.
1999A&A...351..119K    Altcode: 1999astro.ph..3474K
  We report on the first firm detection of pulsed gamma -ray emission
  from PSR B1509-58 in the 0.75-30 MeV energy range in CGRO COMPTEL data
  collected over more than 6 years. The modulation significance in the
  0.75-30 MeV pulse-phase distribution is 5.4sigma and the lightcurve
  is similar to the lightcurves found earlier between 0.7 and 700 keV:
  a single broad asymmetric pulse reaching its maximum 0.38 +/- 0.03 in
  phase after the radio peak, compared to the offset of 0.30 found in
  the CGRO BATSE soft gamma-ray data, and 0.27 +/- 0.01 for RXTE (2-16
  keV), compatible with ASCA (0.7-2.2 keV). Analysis in narrower energy
  windows shows that the single broad pulse is significantly detected
  up to ~ 10 MeV. Above 10 MeV we do detect marginally significant
  (2.1sigma ) modulation with an indication for the broad pulse. However,
  imaging analysis shows the presence of a strong 5.6sigma source at
  the position of the pulsar. To investigate this further, we have also
  analysed contemporaneous CGRO EGRET data (&gt;30 MeV) collected over
  a nearly 4 year period. In the 30-100 MeV energy window, adjacent
  to the COMPTEL 10-30 MeV range, a 4.4sigma source can be attributed
  to PSR B1509-58. Timing analysis in this energy window yields an
  insignificant signal of 1.1sigma , but with a shape somewhat similar to
  that of the COMPTEL 10-30 MeV lightcurve. Combining the two pulse-phase
  distributions results in a suggestive double-peaked pulsed signal above
  the background level estimated in the spatial analyses, with one broad
  peak near phase 0.38 (aligned with the pulse observed at lower energies)
  and a second narrower peak near phase 0.85, which is absent for energies
  below 10 MeV. The modulation significance is, however, only 2.3sigma
  and needs confirmation. Spectral analysis based on the excess counts in
  the broad pulse of the lightcurve shows that extrapolation of the OSSE
  power-law spectral fit with index -1.68 describes our data well up to
  10 MeV. Above 10 MeV the spectrum breaks abruptly. The precise location
  of the break/bend between 10 and 30 MeV depends on the interpretation
  of the structure in the lightcurve measured by COMPTEL and EGRET above
  10 MeV. Such a break in the spectrum of PSR B1509-58 has recently been
  interpreted in the framework of polar cap models for the explanation of
  gamma-ray pulsars, as a signature of the exotic photon splitting process
  in the strong magnetic field of PSR B1509-58. For that interpretation
  our new spectrum constrains the co-latitude to ~ 2degr , close to the
  “classical” radius of the polar cap. In the case of an outer-gap
  scenario, our spectrum requires a dominant synchrotron component.

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Title: Dynamics Of The Internetwork Chromosphere With TRACE
Authors: Krijger, J. M.
1999ESASP.446..391K    Altcode: 1999soho....8..391K
  The UV passbands of the Transition Region and Coronal Explorer
  (TRACE; 170 nm, 160 nm, 155 nm, respectively) sample the low
  chromosphere. Quiet-sun regions display brightness patterning much like
  Ca II H &amp;K, including internetwork grains akin to the so-called K2v
  grains. We demonstrate this pattern correspondence with simultaneous
  TRACE and La Palma data, study and we Fourier-analyze high-cadence
  TRACE image sequences to obtain power, coherence and phase difference
  spectra, separately for network and internetwork.

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Title: COMPTEL Detection of Pulsed Emission from PSR B1509-58 up to
    at Least 10 Mev
Authors: Kuiper, L.; Hermsen, W.; Krijger, J. M.; Bennett, K.;
   Schönfelder, V.; Carramiñana, A.; Manchester, R.; Bailes, M.
1999ApL&C..38...33K    Altcode: 1998astro.ph.12405K
  We report the COMPTEL detection of pulsed $\gamma$-emission from PSR
  B1509-58 up to at least 10 MeV using data collected over more than 6
  years. The 0.75-10 MeV lightcurve is broad and reaches its maximum near
  radio-phase 0.38, slightly beyond the maximum found at hard X-rays/
  soft $\gamma$-rays. In the 10-30 MeV energy range a strong source is
  present in the skymap positionally consistent with the pulsar, but we
  do not detect significant pulsed emission. However, the lightcurve is
  consistent with the pulse shape changing from a single broad pulse
  into a double-peak morphology. Our results significantly constrain
  pulsar modelling.